Chlorinated trisodium phosphates

ABSTRACT

Chlorinated trisodium phosphates of high available chlorine contents are produced by including small percentages, e.g. 0.5 percent of alkali metal silicate, e.g., sodium metasilicate in the batch containing sodium phosphates and sodium hypochlorite under chlorination conditions.

0 United States Patent [15] 3,656,890 Toy et al. v [451 Apr. 18, 1972[54] CHLORINATED TRISODIUM [56] References Cited PHOSPHATES UNITEDSTATES PATENTS [72] g 'g' g' ;j$ 3,525,583 8/1970 Vickers ..23/5o R [73]Assignee: Stouffer Chemical Company, New York, Primary Examiner-"0W8! QAssistant Examiner-Hoke S. Miller Attorney-Wayne C. Jaeschke, Paul J.Juettner and Daniel S, [22] Filed: Sept. 5, 1969 Ortiz [2]] App]. No.:855,751 I ABSTRACT Chlorinated trisodium phosphates of high availablechlorine [52] U.S. Cl. ..23/50 R, 252/99, 24522121279, contents areproduced by including Small percentages, e g 05 percent of alkali metalsilicate, e.g., sodium metasilicate in the [5 I] '3 "Colb 11/00 Aolb1/00 9 25/16- batch containing sodium phosphates and sodium hypochlorite[58] Field of Search ..23/315, 107, 50211523311489 I under chlorinationconditions 6 Claims, No Drawings CHLORINATED TRISODIUM PHOSPHATES Thisinvention relates to the production of chlorinated trisodium phosphates,and more particularly, to chlorinated trisodium phosphates of increasedavailable chlorine content.

The commercial process for making chlorinated trisodium phosphateinvolves adding a solution of sodium hypochlorite to a hot solution ofsodium phosphate. The sodium phosphate solution employed is slightlyless alkaline than a trisodium phosphate and is usually referred to as adi-tri liquor. The hot mixture is permitted to cool and crystallize toform a product which is believed to have the formula 4(Na PO '1lH O)NaOCl. lmpurities also formed in the product include sodium chlorideandNa HPO -2H O. Damp crystals from the batch are passed through a dryer inorder to produce the final crystalline product. One major use of thechlorinated trisodium phosphates is in household cleansers. The productis also used in its unadulterated form as a sterilizing agent in foodprocessing plants, dairies, breweries, etc. The active chlorine isprovided by the NaOClmoiety. The amount of chlorine which is present inactive 'form is referred to as available chlorine. Available chlorine isdefined as twice the stoichiometric amount of chlorine present in themolecule and can be determined by standard methods.

Certain factors have an important influence on available chlorinecontent. These factors include (1) water content of the batch, (2)amount of hypochloride added to the batch, and (3) Na O to P We havediscovered that the addition of certain materials to the batch alsocauses increased percentages of the active chlorine to be retained andto show up as available chlorine in the final product. In the practiceof the present invention, it has been discovered that the addition ofminor percentages of water-soluble alkali metal silicates to the batchof sodium phosphates and sodium hypochlorite substantially improve theavailable chlorine content of the final product.

Suitable water-soluble, alkali metal silicates include the sodium andpotassium metasilicates, e.g. Na SiO sodium ortho silicates such as NaSiO silicates such as K Si O as well as alkaline liquid silicatescontaining varying alkali metal oxide to SiO ratios.

.The process of the present invention is generally carried out byadmixing a solution of sodium phosphate liquor containing a desired Na Oto P 0 ratio and alkali metal hypochlorite in the presence of thedesired percentage of the water-soluble, alkali metal silicate. Thereaction can be carried out either as a batch or as a continuousprocess.

Suitable sources of the sodium phosphate starting material are thosewhich will result in an Na O to P 0 ratio within the desired rangeswhich are broadly 2:1 to about 3:1 and preferably 2.5:1 to about 2.8:l.Sodium phosphate liquors within these ratios are known as di-triliquors. These ratios of Na O to P 0 can be achieved in any suitablemanner, e.g., by mixing ortho phosphoric acid and caustic, Q! by mixingvarious sodium ortho phosphate salts including the monoand diorthophosphates with caustic or with trisodium ortho phosphate. Thesemixtures refer to sodium salts of ortho phosphates.

Reaction conditions preferably include providing a di-tri liquor at anelevated temperature in the proximity of its boiling point in order toprevent crystallization. This hot liquor is preferably provided at atemperature between'about 85 C. and about 1 10 C. and most preferablybetween about 90 C. and about 100 C. at which temperature sodiumhypochlorite is added. Most preferably, the water-soluble alkali metalsilicate is added to the di-tri liquor such that it is completelydissolved and admixed thoroughly therewith prior to addition of thesodium hypochlorite. lf desired, the alkali metal silicate can bedissolved in water prior to admixture with the di-tri liquor. The alkalimetal silicate can also be added to the hypochlorite although thisprocedure is not preferred. When The amount of sodium hypochlorite whichis employed relative to sodium phosphate will depend upon thehypochlorite content which is desired in the final product. Aspreviously mentioned, one of the factors which influences the availablechlorine content is the percentage of sodium hypochlorite which is addedto the mixture. However, at the higher levels, regardless of thepercentage of sodium hypochlorite which is added to the mixture, it hasbeen found that the presence of the alkali metal silicate additiveimproves the chlorine retention in the final product. Generally, theconsumer of this type of product desires to have the highest possibleavailable chlorine content, however, practical limits of availablechlorine are roughly 3 5 percent.

EXAMPLE 1 This example illustrates the preparation of a laboratory batchof chlorinated TSP containing no additive which is employed as areference standard for this work. About 44 grams of 50 percent sodiumhydroxide is mixed with 76 grams of water and heated to about C. in abeaker. Dry particles of Na HPQ, are then added to the caustic watermixture in an amount of about 107 grams over a period of about 5 to 10minutes. The reaction causes the temperature of the resulting mixture torise to just under C. The hot liquor is then pouredinto a Hobartkettle-type mixer. When the temperature of the liquor drops to about 90C., 71 grams of a sodium hypochlorite solution (approximately 24 percentsodium hypochlorite by weight is added. The mixer is permitted tooperate until the contents are cooled and crystallized. The contents ofthe mixer are then removed and air dried for a period of about 30minutes to 1 hour. The available chlorine content is then measured onthe dry product. The determination of available chlorine is that givenin Scans Standard Methods of Chemical Analysis, 5th Ed., Vol. 1, p. 289,under Available Chlorine in Liquid Bleach. Since this material is a dryproduct, the sample is weighed and dissolved rather than using ameasured amount of liquid.

EXAMPLE 2 In this example, the di-tri liquor is prepared in the samemanner as specified in Example -l. Prior to hypochlorite addition,however, 1.5 grams of sodium metasilicate, Na SiO which is in drypowdered form is added to the liquor. Hypochlorite is then added in themanner specified in Example l.

The available chlorine content of the product is determined by themethod referred to in Example 1. In the case of Example l, the availablechlorine content is 4.2 percent and in the case of Example 2, theavailable chlorine content is 4.69 percent by weight.

In order to assess the effect of addition of varying percentages ofalkali metal silicates, additional Example 3 is carried out in themanner described below. It should be noted that the amount of silicateemployed in Example 2 is approximately one-half of 1 percent of thetotal batch. This level of silicate gives a slightly turbid solution.Higher concentrations of silicate would result in even greater turbidityand therefore it is preferred to employ one-half percent or less byweight of the total batch.

EXAMPLE 3 2. This results in an available chlorine content of 4.40.

the components have been admixed, they are permitted to cool whichresults in crystallization of the chlorinated TSP. The crystals are thenpreferably dried and packaged in any desired manner.

EXAMPLE 4 ment. The product is made by running in a premeasured volumeof di-tri liquor at l08 C. into a batch tub. At

this point, additive is introduced into the batch tub which is equippedin a manner to provide intimate mixing of the constituents introducedthereto. Solid sodium metasilicate is employed as the additive. Apremeasured volume of sodium hypochlorite solution is run into the batchtub and the tub is rotated until fairly dry crystals are obtained. Asample is removed and air dried by raking a thin layer of the sample ona sheet of paper. When the samples are thoroughly dried, availablechlorine analyses is determined by the method referred to in Example l.Reference is made to Table I which summarizes the data obtained inaccordance with Example 4 and which indicates improved chlorineretention by reason of the sodium metasilicate additive. This confirmslaboratory results.

EXAMPLE 5 This example is carried out in essentially the same mannerunder the same conditions as specified in Examples 1 and 2 except thatthe alkali metal silicate employed in this case is sodium orthosilicate.It is noted that this additive likewise improved chlorine retention andavailable chlorine in the product.

EXAMPLE 6 This example is carried out in essentially the same manner asExamples 1 and 2 except that a liquid silicate containing approximately9 percent of Na O and 29 percent of SiO, is employed. Using the sameprocedure and quantities of di-tri liquor and hypochlorite as given inExample 1, 2.5 grams of the liquid silicate are added to the hot di-triliquor prior to the hypochlorite addition. The batch is then mixed whileallowing it to cool and crystallize. The damp crystals are dried as inExample 1. It is noted that the addition of liquid silicate alsoimproves the available chlorine content of the dried product over thatof one prepared in like manner but without an additive.

What is claimed is:

1. A method of making chlorinated trisodium phosphate which comprisesadmixing aqueous sodium orthophosphate solution and sodium hypochloriteat a temperature between about C. and about C. in the presence of asmall amount of the order of about 0.5 percent or less by weight of awater-soluble alkali metal silicate, cooling the resultant mixture, andrecovering a crystallized mixture comprising chlorinated trisodiumphosphate.

2. The method of claim 1 in which said silicate is selected from thegroup consisting of sodium and potassium salts of silicates,orthosilicates, metasilicates, and alkaline liquid silicate mixtures.

3. The method of claim 1 in which said silicate is sodium metasilicate.

4. The method of claim 1 in which said silicate is potassiummetasilicate. I I I I I I I 5. The method of claim 1 in which saidsilicate is sodium orthosilicate.

6. The method of claim 1 in which said silicate is an alkaline liquidsilicate mixture.

# 2 3 UNITED STATES PATENT OFFICE,

CERTIFICATE 6F QGRRECHQN Patent No. 5, 656, 90 Q Dated April 18, 1972Inventor) Arthur D. F. Toy and Russell N. Bell It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

On the cover page, Assignee: should read Stauffer delete "Stouffer",

Col. 1, line 27, after (3) insert the ratio of Col. 3, Table 1, line 25,Move up the word metasilicate Signed and sealed this 19th day ofSeptember 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents g;;g UNITED STATES PATENT OFFICE CERTIFICATE OF CO-RRECTIGNPatent No, 5,656,890 Dated April 18, 1972 v fl Arthur D F. Toy andRussell N. Bell c It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

On the cover page, Assignee: should read Stauffer delete "Stouffer" Col.1, line 27, after (5)" insert the ratio of Col. 3, Table 1, line 25,Move up the word metasilicate Signed and sealed this 19th day ofSeptember 1972.

(SEAL) Attest:

ROBERT GOTTSCHALK Commissioner of Patents EDWARD M .FLETCHER,JR.Attesting Officer

2. The method of claim 1 in which said silicate is selected from thegroup consisting of sodium and potassium salts of silicates,orthosilicates, metasilicates, and alkaline liquid silicate mixtures. 3.The method of claim 1 in which said silicate is sodium metasilicate. 4.The method of claim 1 in which said silicate is potassium metasilicate.5. The method of claim 1 in which said silicate is sodium orthosilicate.6. The method of claim 1 in which said silicate is an alkaline liquidsilicate mixture.